层积云共分为（）类。A.5 B.6 C.7 D.8

Many animals  31         (disappear) during the history of the earth.       32          (famous) of these animals were dinosaurs. They lived on the earth        33           (ten) of millions of years ago, long    34        humans came into being. There were many different species of dinosaur and several of them have been found in China. The eggs of twenty-five species have been found in Xixia County, Nanyang, Henan Province, and not long ago a rare new species of bird-like dinosaur was discovered in Chaoyang County, Liaoning Province. The scientists were surprised      35         (find) they could run    36      other dinosaurs, but also climb trees. They could tell this from the way the bones   37          (join) together.

Dinosaurs died    38        quickly about 65 million years ago. Some scientists think it was after a large rock hit the earth and put too much dust into the air. Others think the earth got    39        hot for the dinosaurs to live on any more. Nobody knows   40          sure. In the same way there are animals that have died out more recently and no one knows why. Listen to the story about the dodo, an animal that has disappeared from the earth.

将目标程序中的逻辑地址转换成主存空间的物理地址称为( )。

A．存储分配
B．地址重定位
C．地址保护
D．程序移动

对吸入性麻醉药的作用机制表述正确的是（）

A.作用于中枢特异性受体

B.作用于痛觉中枢

C.其脂溶性影响神经细胞膜脂质，进而暂时改变中枢神经生物膜的功能

D.抑制脑干网状结构上行激活系统

E.作用于大脑皮层

什么是专业档案？

使用平车，经铁路局批准装运《铁路货物运输品名分类与代码表》“04”类的货物按（）计费，超过时按货物重量计费。

A.30t

B.40t

C.50t

D.60t